【Reap】 , 【glean】 ,  【gather】 ,  【garner】 ,  【harvest】  are comparable when they mean to do the work or a given part of the work of collecting ripened crops.

【Reap】 applies to the cutting down and usually collecting of ripened grain; in extension, it may suggest a return or requital.

【Glean】 basically applies to the stripping of a field or vine that has already been gone over once but may be extended to any picking up of valuable bits from here and there and especially to a gathering of what has been left or missed.

【Gather】 , the most general of these terms, applies to the collecting or bringing together of the produce of the farm, plantation, or garden; in extension, it can apply to any similar amassing or accumulating.

【Garner】 implies the storing of produce (as grain); in extension, it can apply to a laying away of a store.

【Harvest】 , the general term, may imply any or all of these processes or be extended in meaning to apply to any gathering together or husbanding.